For printers that print labels or tags or repeatedly print data on a conventional continuous sheet for each of predetermined divisions to prepare paper slips, the sheet position must be accurately grasped so that the labels, tags, or predetermined divisions of the continuous sheet can be printed appropriately. Therefore, a continuous sheet with position detection marks is used in the printing of this type. The marks on this continuous sheet may be black marks, holes, or notches. In the case of a continuous sheet such as a label sheet, in which labels are arranged at regular intervals on a mount, on the other hand, the marks may be gaps between the labels. Many of these marks are configured to vary received light outputs from photoelectric elements.
If a sheet position detection sensor fails to detect a position detection mark during a printing operation for any reason, according to the printer of the type described above, it is concluded that a sheet position detection error has occurred, and the printing operation is stopped thereafter. Specifically, if the sheet position detection sensor can normally detect none of the marks due to a probably instantaneous unexpected cause, such as disturbance light, defective printing of black marks, defective perforation, etc., the printing operation of the printer is inevitably interrupted (even though the next mark may have been normally detected).
While printers that print a continuous sheet with position detection marks are described in the following patent documents, none of them deal with the aforementioned problems.
A printer that prints a label sheet is described in, for example, Japanese Patent Application Laid-Open No. 07-196237. This printer is designed so that the presence of the label sheet itself and printing positions on labels are detected by using a single sheet detection means (or sensor), whereby the equipment costs and production costs can be reduced.
Another printer that prints a label sheet is described in Japanese Patent Application Laid-Open No. 04-323071. This printer is designed to solve a problem associated with the timing of origination of a status signal for a “paper end error”. Even if the error signal is inputted while the label sheet is being printed, the status signal for the “paper end error” is originated to stop the printing operation after the label printing is finished, without stopping the printing operation on the spot.
Described in Japanese Patent Application Laid-Open No. 04-347670 is a system for preventing paper jam that is peculiar to label sheets by stopping issuance (printing) of labels if no label sheet is detected by a sensor while a cutter is being operated.
Printers described in Japanese Patent Applications Laid-Open Nos. 04-275172, 05-084995 and 2002-205872 can use both ordinary continuous sheets without position detection marks and label sheets (each formed of a continuous mount and a plurality of labels thereon). In these printers, a sheet feed mode is established by automatically making discrimination between ordinary continuous sheets and label sheets, so that it is unnecessary to manually reset the printers with every change of the sheet type.